U.S. Pat. No. 3,129,891 issued Apr. 21, 1964, discloses a fuel nozzle assembly having primary and secondary fuel flow paths with a metering valve in the secondary flow path. A tubular fuel filter is employed to filter fuel flowing to the secondary metering valve while vortex action in an outer concentric swirl chamber in combination with outer circumferential dirt entrapping is used to prevent passage of major size dirt particles to the nozzle tip.
U.S. Pat. No. 3,443,760 issued to Simmons illustrates a fuel nozzle assembly having a fuel strainer for fuel flowing to a secondary metering valve. U.S. Pat. Nos. 3,022,954 to Davies; 3,154,095 to Cleminshaw and 2,954,172 to Grundman illustrate filter and metering valve arrangements.
U.S. Pat No. 4,491,272 issued to Jerome R. Bradley et al of common assignee shows a fuel valve assembly in which a stationary tubular fuel filter between a check valve and metering valve in a main valve housing filters fuel flow to a primary fuel flow path and is washed by fuel flow discharging from an upstream check valve when both primary and secondary fuel are flowing.